So here's the deal. I made this website
for my Liquid
Helium customers at the University of Florida.
It used to include more information explaining the comparison claim.
But, because in the explaination, I insulted
a lab for being foolish, I had to remove the offending material.
But now, this page is mostly found via internet search engines for
"cost of helium."
I assume what you are looking for is where you can buy helium and how
much it costs.

The typical way to get helium is in high pressure gas cylinders
available from welding supply companies.
Just about anyone can get helium from a welding supply store, but IT
CAN KILL YOU. It is not a toy.
These are the cylinders you see at balloon filling places. They contain
~300 standard cubic feet of helium.(scf)
So you could fill about 300 balloons with of about a one foot diameter.
The helium would cost about
$100 for the cheapest
purity of helium, but you need to put a deposit on the cylinder (~$150)
and you need a balloon filler regulator. (~$100US, ~$15US on eBay)
For other uses you will need an inert gas regulator (~$100-$300US).
Other higher purities of helium are available in the same type cylinder
packages for more money.
Do a search for "welding supplies" in your area or in the Yellow Pages.
Wal-mart used to
sell smaller, cheaper tanks, with much less helium in them for ~$25US
in their stores, but I think they have stopped.Amazon.com
sells the small tanks of helium. (~$70 plus shipping) from Worthington
Cylinders.Tank
can fill approximately (50) - 9" latex balloons, or (27) - 11" latex
balloons with a float time of approximately 5-7 hours, or (27) - 18"
Foil Balloons, or (20) - 20" Foil Balloons with a float time of
approximately 4 days. Tank holds approximately 14.9 cubic feet of
helium.

Commercial
quantities are available from major gas suppliers; Praxair, BOC, Air
Products, Air Liquide. They are the suppliers to the local welding
supply companies.

They also sell liquid helium. But it is very unlikely that you need
this. At least ~$7.00US/liquid liter (usually much higher) in 100 liter
or more quantities in
the US but much more expensive elsewhere.